Wireless communication, e.g., mobile radio-frequency (RF) telecommunication, positioning and/or networking, has becomes an essential portion of contemporary information society. Wireless communication is implemented by associated wireless device, e.g., mobile phone, cellular phone or portable computer, compliant to specification (standards and/or protocols) of the wireless communication. Hence, how to reduce design, assembling and/or manufacturing effort and cost of wireless device, as well as how to enhance performance of wireless device, have become key challenges for modern electrical engineering.
To accomplish successful wireless communication, wireless device is expected to receive faint wanted wireless signal correctly (e.g., below a given block error rate, BLER) against interference of unwanted wireless signal, e.g., a strong continuous-wave (CW) blocking signal also referred to as blocker, which presents near frequency band (in-band) allocated to the wanted wireless signal. Specification of modern wireless communication includes stringent blocking standards to be followed by compliant wireless device. For example, FIG. 1 and FIG. 2 respectively illustrate two blocking standards for low-band EDGE MCS 4 GSM 850 and high-band PCS developed by ETSI, wherein GSM, EDGE, MCS, PCS and ETSI respectively are abbreviations of “global system for mobile communication,” “enhanced data rates for GSM evolution,” “modulation and coding scheme,” “personal communication service” and “European telecommunications standards institute.”
As shown in FIG. 1, the frequency domain is divided to an in-band portion between frequencies fa1 and fd1 (e.g., 849 and 914 MHz) allocated for wanted wireless signal, an out-of-band (OOB) portion OOB(a) below the frequency fa1 (to about 200 MHz) and an OOB portion OOB(d) above the frequency fd1 (to about 12.75 GHz). The blocking standard shown in FIG. 1 demands a compliant wireless device to receive a wanted wireless signal of −99 dBm at a frequency f0 of the in-band portion with BLER below 10% when an unwanted blocker of 0 dBm presents at a frequency of the portions OOB(a) and OOB(d).
In the example of FIG. 2, the frequency domain is divided to an in-band portion and four OOB portions OOB(a) to OOB(d). The portion OOB(a) is below a frequency fa2 (e.g., 1830 MHz), the portion OOB(b) is between the frequency fa2 and a frequency fb2 (e.g., 1910 MHz), the in-band portion is between the frequency fb2 and a frequency fc2 (e.g., 2010 MHz), the portion OOB(c) is between the frequency fc2 and a frequency fd2 (e.g., 2070 MHz), and the portion OOB(d) is above the frequency fd2. For a wireless device to be compliant with the blocking standard shown in FIG. 2, a wanted in-band wireless signal of −99 dBm is expected to be received with BLER below 10% when an unwanted blocker of 0 dBm presents at a frequency of the portions OOB(a) and OOB(d), and/or an unwanted blocker of −12 dBm presents at a frequency of the portions OOB(b) and OOB(c).
From the examples of FIG. 1 and FIG. 2, it is noted that OOB portions (i.e., the portions OOB(a) and/to OOB(d)) cover a broad range of the whole frequency axis, and OOB blocker can present at any frequency in the OOB portions. That is, a compliant wireless device is demanded to reject blockers at a wide variety of frequencies.
Conventionally, the rather challenging blocking standard is overcome by adopting an external, bulky but expensive SAW (surface acoustic wave) filter, or by adopting a highly linear differential receiver which requires a cooperative external BALUN. Although off-chip SAW filter(s) or BALUN(s) may contribute to suppression of blockers, both incur extra costs. Furthermore, to implement the external SAW filter and/or BALUN, extra impedance matching components (networks) are needed, which also add on the overall cost. In addition, system designer of wireless device needs more design effort, know-how and experience to properly place and route the external SAW filter(s) and/or BALUN(s) along with the accompanying impedance matching components on circuit board, e.g., printed circuit board (PCB). Even with fully devoted effort, the resultant PCB placement and routing are sensitive to variations, and lack flexibility and/or reusability to be generally adopted by different types of devices.
Please refer to FIG. 3 illustrating a conventional wireless interface (platform) 10 for a wireless device. The interface 10 bridges an antenna 16 to a transmitter 24a and a receiver 24b, and includes a transmit module (a packaged IC) 14, an external BALUN (another packaged IC) 20, off-chip capacitors C122 and C125, and networks 12, 18 and 22. The network 12 includes off-chip resistors R81 and R82, and capacitors C119 and C121. The network 18 includes off-chip capacitors 123, 124, 126 and 127, along with inductors L16 and L17. The network 22 includes off-chip inductors L13 to L15 and L18 to L22. The off-chip capacitors, inductors and resistors of the networks 12, 18, and 22, as well as the transmit module 14, BALUN 20 and the capacitors C122 and C125, are collectively mounted on a circuit board (e.g., PCB, not shown) of the wireless device.
The transmit module (TxM) 14 includes an antenna switching module (ASM, not shown), so a terminal ANT electrically coupled to the antenna 16 can be selectively conducted to one of terminals Rfin_HB, Rfin_LB, RX0 and RX1. High-band RF signal and low-band RF signal to be transmitted via the antenna 16 are provided by the transmitter 24a respectively via terminals HB_TX and LB_TX, relayed to the terminals Rfin_HB and Rfin_LB via the network 12, and further relayed to the antenna 16 via the TxM 14.
On the other hand, high-band wireless RF signal and low-band wireless RF signal received via the antenna 16 are respectively dispatched to the terminals RX0 and RX1, and relayed to terminals HBin and LBin of the BALUN 20 as two single-end signals via the capacitors C125, C122 and the network 18, which serves as an ASM matching network. The BALUN 20 can convert the single-end signal at the terminal LBin to a differential signal between terminals LBout+ and LBout−, and convert the single-end signal at the terminal HBin to another differential signal between terminals HBout+ and HBout−. Further via the network 22 which serves as a receiver differential matching network, the two differential signals between the terminals LBout− and LBout+ as well as the terminals HBout+ and HBout− are respectively relayed to terminals LB_RX_P, LB_RX_N, HB_RX_P and HB_RX_N to be received by the receiver 24b. 
According to FIG. 3, it is noted that the external BALUN 20 needs fourteen components (inductors and capacitors) to implement the network 22 between the BALUN 20 and the receiver 24b, and the network 18 between the BALUN 20 and the TxM 14.